As is well known, blast furnaces generally comprise multiple fluid injection paths, whereby hot gas is injected into the blast furnace via blowpipes and tuyeres. If material has accumulated in front of the tuyere nozzle, an injection port may be blocked. If left undetected, the fluid may no longer exit the blowpipe, thus not being fed into the blast furnace. Furthermore, tuyeres are often used to feed pulverized coal into the blast furnace. Should an injection port be blocked this would of course prevent pulverized coal to enter the blast furnace and may cause an accumulation of the pulverized coal in the tuyere and the blowpipe.
In order to observe whether or not a tuyere is blocked, a tuyere sight hole, often also referred to as a peephole or peep sight, is arranged at the rear end of the blowpipe. Such a peep sight allows an operator to look right through the blowpipe and the tuyere zone, thus inspecting the condition of the tuyere and detecting if a blockage has occurred in the tuyere zone.
The tuyere also provides a window into the interior of the blast furnace. Thus, the peep sight also allows observing internal conditions of the blast furnace. The peep sight therefore allows monitoring the condition and the temperature evolution in the heart of the blast furnace. The operator can thus detect disfunctionings in the operation of the blast furnace and act accordingly.
In order to facilitate monitoring and provide for a more automated system, electronic monitoring devices, such as tuyere video cameras have been developed which continuously monitor the light emitted through the peep sight and provide feedback to the operator.
In order to allow both monitoring systems to work simultaneously, i.e. allow visual monitoring with the naked eye and electronic monitoring, a light deflector can be installed to deflect part of the incident light towards the electronic monitoring device while allowing part of the light to pass to the peep sight for visual monitoring. In order for such a light deflector to adequately direct light to both the electronic monitoring device and the peep sight, the orientation of the light deflector is of importance. An adjustment mechanism for the light deflector is thus beneficial, in particular because there may be relative movement between the various components due to important temperature differences of the blast furnace installation. Indeed, generally the electronic monitoring device, the peep sight and the light deflector would be installed while the blast furnace is at a standstill. As the blast furnace is brought up to its working temperature, this temperature difference causes relative movement between various elements and may cause misalignment of the light deflector. Adjustment of the light deflector then becomes necessary. Also, the adjustment of the light deflector may be useful to compensate for any constructional geometrical errors that may occur during production of the monitoring system.
In LU 90 610, an optical sensor is arranged perpendicular to the light path from the tuyere to the peep sight. A light deflector formed by a glass plate is arranged in a cylindrical housing to deflect part of the light to the optical sensor. The glass plate forms an angle of about 45° with respect to the light path between the tuyere to the peep sight. For adjusting means, the glass plate can be independently rotated in two directions inside the cylindrical housing. An eccentric screw can set the position of a first support plate, mounted rotatably around an axis perpendicular to the central axis on a rear face of the cylindrical housing. A second adjustment screw allows together with a spring a second support plate, mounted on the first support plate, to swivel the glass plate about a swiveling axis. As LU 90 610 requires access to two separate adjustment screws arranged within the housing, its adjustment mechanism may be considered cumbersome by some.